Past studies on the relationship between mutational voice change and body growth were generally made on grouped subjects and no exact longitudinal observation was performed. In the present report, a longitudinal study was made on 100 young male students in their puberty, in which voice recordings and measurements of physical parameters including body height and weight were performed twice for each subject with yearly interval. Information on subjective evaluation of voice abnormality was also obtained from each subject. The recorded voice samples were subjected to subsequent analysis for obtaining fundamental frequency (F0) and formant values. The following results were obtained.
1. A negative correlation in the rate of change was observed between F0 and physical parameters such as body height and weight, and sitting height.
2. It was suggested that the mutational period consisted of the rapid and slow phases. The rate of growth in body height and sitting height was more significant in the rapid phase. 3. Subjective voice abnormality and physical growths such as the development of the laryngeal prominence were often noted even before the rapid phase. After the rapid phase was over, all the cases showed secondary sexual characteristics including the laryngeal prominence.
4. Before and during the rapid phase, there was a tendency for the values of F1 and F2 to increase, while that of F3 to decrease. After the rapid phases was over, there was a trend that F1 and F2 increased, while F3 remained unchanged.